Also, DL flies JFK-PSA (I forgot about that one earlier) so while is is hypothetically a couple extra hours of flying (~1000 miles) to go via NYC, it is also one fewer connection and probably a shorter total travel time because of the "missing" layover.

Also remember that you can mix and match, so you could do SEA-JFK-PSA on the outbound on DL and FLR-CDG-SFO-SEA on the return using the routing I suggested above.